I am a developer and IT manager/director in Berlin.
I will say this: in most small to medium IT companies (in Berlin) a cover letter is not needed or even wanted in most cases -- speak with your work and your CV. The cover letter is just excess "stuff" that we have to read on top of everything else. Larger corporations may appreciate this more.
A CV should be kept VERY short and to the point (i.e. 1-2 pages). A "creative" CV is fine if you are applying for a creative position, but outside of that keep it simple and avoid being confusing. Note that Germany has its own CV format which often includes your picture, marital status, and so forth. Adhering to this is a plus in most cases!
Example projects you participated in (such as a URL to a site you developed) or code samples (i.e. GitHub) are an enormous plus that will put you at the front of the line (if it is good code, naturally).
If you are applying from outside the EU, it is important to stand out because of the extra cost and process (which is relatively quick and painless in Germany compared to some other countries, such as England) for your visa and residency. There is, however, a large shortage of talented IT professionals here and most companies regularly seek out candidates from outside Germany and even outside the EU.
In Berlin, you can likely get away with not speaking German, though it is a "plus." In many parts of Germany (i.e. Munich), the majority of positions will require/assume you speak German plus some level of English proficiency.